All of the elements you see can be found in Design’s default brush strokes:

To create similar brush effects, simply draw strokes and increase the width until you get the desired effect. Then to manipulate further, select Object/Convert Stroke to Path. For example, I didn’t want as many large stars as the brush gave me so after converting to path I just deleted the extras. This works great for adding abstract elements to a background or creating wallpapers.

Hope you like it, and if you have any questions, feel free to leave a comment below!